There are many possible ways to provide a roof for a structure. One way to roof a structure is through the use of metallic roofing panels. The art of roofing structures with metallic roofing panels has advanced to the use of standing seam roofing panels. Standing seams are formed when raised longitudinal edges of roofing panels engage to form a longitudinal ridge running from the peak to the gutter of a roof.
Standing seam metallic roofing panels are normally manufactured from galvanized steel or GALVALUME (TM) and then may be painted or coated with a protective film. The individual panels may vary in width from one to several feet, and may be up to thirty feet in length.
In erecting a structure, walls or columns of the building are first built and rafters, which form the primary roof support, are carried by the walls or columns. These rafters usually span the width of the structure. Joists, or purlins, are load across the rafters, are supported by the rafters, and are normally installed perpendicularly to the rafters, thereby defining the roof line. The purlins extend along the length of the building. Insulation may be laid across the joists.
A standing seam roofing system may then be installed. Roofing panels are joined together along adjacent longitudinal sides in a male/female joint to form the standing seams. It is known in the art how to attach the roofing panels to the joists, or purlins.
In structures where the distance from the peak to the gutter line is greater than the maximum length of a single roofing panel, it may be necessary to install two or more lengths of roofing panels to provide a roof. Endlap joints are formed where the end of one panel overlaps the end of an abutting panel. It will be understood by one skilled in the art that the lower end of the roofing panel, located nearest to the peak of a roof, will overlap the upper end of an abutting roofing panel, located closer to the gutter line of the roof, in a shingle-like manner.
At the point where the two roofing panels overlap, creating an endlap joint, it is necessary to secure the panels together in order to maintain the structural integrity of the roof and to provide a weatherproof seal between the panels. In Gulf Coast aareas where frequent high winds and heavy rains are experienced, it is necessary to maintain an endlap joint that can provide a seal against driving rain and still be strong enough to resist the lifting force of high winds. Very frequently, the atmosphere in the interior of the structure may be air-conditioned. In the process of doing this, the atmospheric pressure may become greater than the pressure in the building and rain-water running over the roof may be sucked through the endlap joint if the joint is not watertight.
In areas of the countery where roofing systems experience seasonal snow loadings, it is imperative to provide an endlap joint of sufficient strength to resist the occasionally high stresses placed on the roof by the snow in order to protect the structural integrity of the roof.
Finally, the endlap joint formed by the overlapping roofing panels must be strong enough to resist "live loads" occasioned by workmen walking on the roof during maintenance of the structure.
The present invention provides a means for creating an endlap joint between overlapping roofing panels that provides structural strength to the roofing system while maintaining a watertight seal against environmental forces.